Aging Behavior of Al-Mg-Si Alloys Processed by High-Pressure Torsion

This research investigates simultaneous strengthening by grain refinement and fine precipitation in age-hardenable Al-Mg-Si alloys containing an additional element of either Ag, Cu, Pt or Pd. The alloys were solution-treated and processed by high-pressure torsion (HPT) at room temperature under a pressure of 6 GPa. They were aged at a temperature of 373 K for up to a total period of 6.7 hours. Vickers microhardness was measured after selected periods of aging and the microstructures were observed by transmission electron microscopy. It was found that, in all alloys, the grain sizes after HPT were refined to 300-400 nm and there were significant increases in the hardness through the HPT processing. The hardness was further increased by the subsequent ageing treatment, confirming the simultaneous strengthening by grain refinement and fine precipitation. However, the aging behavior was different depending on the alloying compositions.

Download Full-text

Omega Phase Formation in Ti–3wt.%Nb Alloy Induced by High-Pressure Torsion

Materials ◽

10.3390/ma14092262 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2262

Author(s):

Anna Korneva ◽

Boris Straumal ◽

Askar Kilmametov ◽

Alena Gornakova ◽

Anna Wierzbicka-Miernik ◽

...

Keyword(s):

Electron Microscopy ◽

High Pressure ◽

Phase Transformations ◽

Grain Refinement ◽

High Pressure Torsion ◽

Β Phase ◽

Ω Phase ◽

Α Phase ◽

Transmission Electron ◽

Different Temperatures

It is well known that severe plastic deformation not only leads to strong grain refinement and material strengthening but also can drive phase transformations. A study of the fundamentals of α → ω phase transformations induced by high-pressure torsion (HPT) in Ti–Nb-based alloys is presented in the current work. Before HPT, a Ti–3wt.%Nb alloy was annealed at two different temperatures in order to obtain the α-phase state with different amounts of niobium. X-ray diffraction analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied for the characterisation of phase transitions and evolution of the microstructure. A small amount of the β-phase was found in the initial states, which completely transformed into the ω-phase during the HPT process. During HPT, strong grain refinement in the α-phase took place, as did partial transformation of the α- into the ω-phase. Therefore, two kinds of ω-phase, each with different chemical composition, were obtained after HPT. The first one was formed from the β-phase, enriched in Nb, and the second one from the α-phase. It was also found that the transformation of the α-phase into the ω-phase depended on the Nb concentration in the α-Ti phase. The less Nb there was in the α-phase, the more of the α-phase was transformed into the ω-phase.

Download Full-text

Aging Behavior of Cu-Ni-Si Alloy Processed by High-Pressure Torsion

Materials Science Forum ◽

10.4028/www.scientific.net/msf.667-669.307 ◽

2010 ◽

Vol 667-669 ◽

pp. 307-312 ◽

Cited By ~ 1

Author(s):

Hirotaka Matsunaga ◽

Z. Horita ◽

Kazutaka Imamura ◽

Takanobu Kiss ◽

Xavier Sauvage

Keyword(s):

Electrical Conductivity ◽

High Pressure ◽

High Pressure Torsion ◽

Three Dimensional ◽

Aging Treatment ◽

Atom Probe ◽

Appreciable Amount ◽

Aging Behavior ◽

Transmission Electron ◽

20 Nm

An age-hardenable Cu-2.9%Ni-0.6%Si alloy was subjected to high-pressure torsion. Aging behavior was investigated in terms of hardness, electrical conductivity and microstructural features. Transmission electron microscopy showed that the grain size is refined to ~150 nm and the Vickers microhardness was significantly increased through the HPT process. Aging treatment of the HPT-processed alloy led to a further increase in the hardness. Electrical conductivity is also improved with the aging treatment. It was confirmed that the simultaneous strengthening by grain refinement and fine precipitation is achieved while maintaining high electrical conductivity. Three dimensional atom probe analysis revealed that fine precipitates with sizes of ~20 nm or smaller were formed in the Cu matrix and some particles consist of Ni and Si with no appreciable amount of Cu.

Download Full-text

Microstructure and Aging Behavior of Cu-Be Alloy Processed by High-Pressure Torsion

Materials Science Forum ◽

10.4028/www.scientific.net/msf.783-786.2707 ◽

2014 ◽

Vol 783-786 ◽

pp. 2707-2712 ◽

Cited By ~ 6

Author(s):

Chihiro Watanabe ◽

Ryoichi Monzen ◽

Seiichiro Ii ◽

Koichi Tsuchiya

Keyword(s):

High Pressure ◽

Room Temperature ◽

High Pressure Torsion ◽

Applied Pressure ◽

Solution Treatment ◽

Equivalent Strain ◽

Aging Behavior ◽

Fine Grained ◽

Transmission Electron ◽

Fine Grained Structure

The microstructure and aging behavior of Cu-1.8wt%Be-0.2wt%Co alloy specimens processed by high-pressure torsion (HPT) at room temperature (RT) and 150°C after solution treatment have been studied. Application of HPT processing at RT and 150°C under an applied pressure of 5 GPa for 10 revolutions at 1 rpm to alloy specimens (RT-and 150°C-specimen) produces an ultra-fine grained structure with a grain size of 70 nm. The hardnesses of the RT-and 150°C-specimens increase with equivalent strain up to 7 and then saturate at constant values of 400 and 430 Hv, respectively. Annealing the RT-specimen at 150°C for 10 min increases the hardness from 400 to 430 Hv. Transmission electron microscopy observations of the 150°C-specimen and the RT-specimen annealed at 150°C reveal that there are no intragranular and intergranular precipitates. It is suggested that the higher hardness of the 150°C-specimen than the RT-specimen is ascribed to the segregation of Be atoms on dislocations during HPT processing at 150°C. The RT-and 150°C-specimens harden rapidly and exhibit maximum values of hardness at 3 min during aging at 320°C. The increase in the hardness is attributed to the precipitation of finely dispersed G.P. zones.

Download Full-text

Microstructure and Tribological Properties of Sub-Microcrystalline Carbon Steel Produced by Severe Plastic Deformation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.876.3 ◽

2018 ◽

Vol 876 ◽

pp. 3-8

Author(s):

Hirotaka Kato ◽

Kouhei Yamashita ◽

Eisuke Sentoku ◽

Yoshikazu Todaka

Keyword(s):

Plastic Deformation ◽

High Pressure ◽

Carbon Steel ◽

Grain Refinement ◽

Sliding Wear ◽

Size Range ◽

High Pressure Torsion ◽

Wear Properties ◽

Grain Sizes ◽

Hardness Values

The microstructure, hardness, and sliding wear properties of high-pressure torsion (HPT)-processed pure Fe and S45C carbon steel were comprehensively investigated. The grains of Fe and S45C were significantly refined to the submicron size range using the HPT process, and the grain sizes were found to decrease with an increased number of turns (N). The Vickers hardness of HPT-processed specimens increased with increasing N or with distance from the center (i.e., with an increase in the strain), which is attributed to grain refinement. In addition, the hardness of HPT-processed Fe was saturated with a further increase in the number of turns owing to the saturation of grain refinement. However, saturation with hardening was not observed in the case of S45C and the hardness values of S45C were much higher than those of Fe. The wear amount was considerably reduced by HPT processing for both Fe and S45C. A linear correlation was determined between the specific wear rate and the inverse of hardness, which agrees with the Archard wear equation. The experimental results show that the reduction in the wear of Fe and S45C is considered to be due to hardening by the HPT process.

Download Full-text

Mechanical Properties of Al-6061 and an Al-6061 Metal Matrix Composite Processed by High-Pressure Torsion

Materials Science Forum ◽

10.4028/www.scientific.net/msf.667-669.689 ◽

2010 ◽

Vol 667-669 ◽

pp. 689-694 ◽

Cited By ~ 1

Author(s):

Cheng Xu ◽

Z. Horita ◽

Terence G. Langdon

Keyword(s):

Mechanical Properties ◽

High Pressure ◽

Metal Matrix Composite ◽

Matrix Composite ◽

Metal Matrix ◽

High Pressure Torsion ◽

Nanometer Scale ◽

Al 6061 ◽

Grain Sizes ◽

Transmission Electron

It is now well established that the application of high-pressure torsion (HPT) leads to exceptionally small grain sizes in bulk solids, usually in the nanometer scale. The HPT method thus attracts considerable attention and has been utilized in processing many materials such as pure metals, alloys and even ceramics. This paper describes experiments conducted on samples of an Al-6061 alloy and an Al-6061 metal matrix composite, reinforced with 20 vol.% Al2O3 particulates, in order to evaluate the mechanical properties of the alloy and its composite processed by HPT. The tensile properties of the materials were obtained both at room temperature and at 773 K and representative microstructures were observed using transmission electron microscopy.

Download Full-text

GRAIN REFINEMENT AND MICROSTRUCTURE EVOLUTION IN ALUMINUM A2618 ALLOY BY HIGH-PRESSURE TORSION

Jurnal Teknologi ◽

10.11113/jt.v78.9163 ◽

2016 ◽

Vol 78 (6-9) ◽

Author(s):

Intan Fadhlina Mohamed ◽

Seungwon Lee ◽

Kaveh Edalati ◽

Zenji Horita ◽

Shahrum Abdullah ◽

...

Keyword(s):

Plastic Deformation ◽

High Pressure ◽

Grain Refinement ◽

Room Temperature ◽

Rotation Speed ◽

High Pressure Torsion ◽

Applied Pressure ◽

Saturation Level ◽

Microstructural Refinement ◽

Average Grain Size

This work presents a study related to the grain refinement of an aluminum A2618 alloy achieved by High-Pressure Torsion (HPT) known as a process of Severe Plastic Deformation (SPD). The HPT is conducted on disks of the alloy under an applied pressure of 6 GPa for 1 and 5 turns with a rotation speed of 1 rpm at room temperature. The HPT processing leads to microstructural refinement with an average grain size of ~250 nm at a saturation level after 5 turns. Gradual increases in hardness are observed from the beginning of straining up to a saturation level. This study thus suggests that hardening due to grain refinement is attained by the HPT processing of the A2618 alloy at room temperature.

Download Full-text

The Processing of Ultrafine-Grained Materials Using High-Pressure Torsion

Materials Science Forum ◽

10.4028/www.scientific.net/msf.558-559.1283 ◽

2007 ◽

Vol 558-559 ◽

pp. 1283-1294 ◽

Cited By ~ 1

Author(s):

Cheng Xu ◽

Z. Horita ◽

Terence G. Langdon

Keyword(s):

Plastic Deformation ◽

Grain Size ◽

High Pressure ◽

High Pressure Torsion ◽

Metallic Materials ◽

Grain Sizes ◽

Ultrafine Grained ◽

Wide Range ◽

Ultrafine Grained Materials ◽

Thin Disks

It is now well-established that processing through the application of severe plastic deformation (SPD) leads to a significant reduction in the grain size of a wide range of metallic materials. This paper examines the fabrication of ultrafine-grained materials using high-pressure torsion (HPT) where this process is attractive because it leads to exceptional grain refinement with grain sizes that often lie in the nanometer or submicrometer ranges. Two aspects of HPT are examined. First, processing by HPT is usually confined to samples in the form of very thin disks but recent experiments demonstrate the potential for extending HPT also to bulk samples. Second, since the strains imposed in HPT vary with the distance from the center of the disk, it is important to examine the development of inhomogeneities in disk samples processed by HPT.

Download Full-text